Genetic study of non-syndromic tooth agenesis through the screening of paired box 9, msh homeobox 1, axin 2, and Wnt family member 10A genes: a case-series.

Non-syndromic tooth agenesis (NSTA) is the most common developmental anomaly in humans. Several studies have been conducted on dental agenesis and numerous genes have been identified. However, the pathogenic mechanisms responsible for NSTA are not clearly understood. We studied a group of 28 patients with sporadic NSTA and nine patients with a family history of tooth agenesis. We focused on four genes - paired box 9 (PAX9), Wnt family member 10A (WNT10A), msh homeobox 1 (MSX1), and axin 2 (AXIN2) - using direct Sanger sequencing of the exons and intron-exon boundaries. The most prevalent variants identified in PAX9 and AXIN2 genes were analyzed using the chi-square test. The sequencing results revealed a number of variants in the AXIN2 gene, including one novel missense mutation in one patient with agenesis of a single second premolar. We also identified one variant in the AXIN2 gene as being a putative risk factor for tooth agenesis. Only one missense mutation was identified in the WNT10A gene and this mutation was found in two patients. Interestingly, WNT10A is reported as the most prevalent gene mutated in the European population with NSTA.

Characterization of a novel mutation in PAX9 gene in a family with non-syndromic dental agenesis.

BACKGROUND: Dental agenesis is the most common developmental anomaly in man and may present either as an isolated trait or as part of a syndrome, such as ectodermal dysplasia. Until now, the underlying molecular pathogenic mechanisms responsible for dental agenesis are still largely unknown. Several genetic and molecular studies have demonstrated that at least 300 genes are involved in tooth formation and development, coding for specific transcriptional factors, receptors or growth factors that are expressed at specific developmental stages. Dental agenesis in this respect is believed to result from altered expression of one or more of these factors during initiation and early morphogenesis of the tooth germ, and the first actors identified were MSX1 and PAX9. DESIGN: In this study, we focalized on a Tunisian family with a non-syndromic autosomal dominant form of tooth agenesis. In order to screen for the eventual genetic cause of dental agenesis in this family we sequenced 4 genes; PAX9, WNT10A, MSX1 and AXIN2 using Sanger sequencing. RESULTS: Direct Screening analysis of PAX9 gene, revealed a novel mutation p.Asp200Serfs*13. It consists of a duplication of 5 basepairs leading to a codon stop 13 position downstream. This novel mutation was found in all affected family members. CONCLUSIONS: In this report, we present the first genetic study of a Tunisian family with a non-syndromic autosomal dominant form of tooth agenesis, in which we identified in PAX9 gene a novel mutation. It most likely results in nonsense mediated RNA decay and haploinsifficiency that reduce the transactivation capacity of PAX9.

Partial KCNQ1OT1 hypomethylation: A disguised familial Beckwith-Wiedemann syndrome as a sporadic adrenocortical tumor.

Beckwith-Wiedemann syndrome has a wide spectrum of complications such as embryonal tumors, namely adrenocortical tumor. Tumor predisposition is one of the most challenging manifestations of this syndrome. A 45-day old female with a family history of adrenocortical tumor presented with adrenocortical tumor. The case raised suspicion of a hereditary Beckwith-Wiedemann syndrome, therefore molecular analysis was undertaken. The results revealed partial KCNQ1OT1 hypomethylation in the infant's blood DNA which was associated with a complete loss of methylation in the infant's adrenocortical tumor tissue. It is unique for familial Beckwith-Wiedemann syndrome caused by KCNQ1OT1 partial hypomethylation to manifest solely through adrenocortical tumor. Incomplete penetrance and specific tissue mosaicism could provide explanations to this novel hereditary Beckwith-Wiedemann syndrome presentation.

Modulation at age of onset in tunisian huntington disease patients: implication of new modifier genes.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. The causative mutation is an expansion of more than 36 CAG repeats in the first exon of IT15 gene. Many studies have shown that the IT15 interacts with several modifier genes to regulate the age at onset (AO) of HD. Our study aims to investigate the implication of CAG expansion and 9 modifiers in the age at onset variance of 15 HD Tunisian patients and to establish the correlation between these modifiers genes and the AO of this disease. Despite the small number of studied patients, this report consists of the first North African study in Huntington disease patients. Our results approve a specific effect of modifiers genes in each population.